The present invention is directed toward a method for adhering a material to coat at least one surface of a densified random-fiber composite sheet. The method provides for a fibrous surface to which coating materials can physically interact to firmly bond thereto. More specifically, the fibers present in the composite sheet are caused to project outward from the plane defined by the surface of the sheet to form an activated surface. The fibers are activated by heating said surface either prior to or simultaneously with the application of the coating material.
Generally, densified random-fiber composite sheets are prepared from fibrous reinforcement materials, binders and a heat-fusible organic polymer. These polymeric composite sheets exhibit the excellent properties of the polymer from which they are designed plus increased physical properties (see generally, U.S. Pat. No. 4,426,470). While the polymeric composites exhibit excellent properties it can be difficult to adhere other materials to the polymeric surface of the composite sheet. Thus, a method for adhering other materials to random-fiber composite sheets is very desirable.
It has been discovered that predensified random-fiber composite sheets (hereinafter "composite sheet") can be treated such that they offer an excellent surface to which coating materials can physically interact to form excellent bonds. This method therefore allows composite sheets to be employed in a wide range of applications heretobefore deemed to be quite difficult. Additionally, the subject method allows various adhesive coating materials to be employed with composite sheets to more fully utilize the potential of composite sheets.